Memory devices are typically provided as internal, semiconductor, integrated circuits in computers or other electronic devices. There are many different types of memory including volatile and non-volatile memory. Volatile memory can require power to maintain its data (e.g., host data, error information, etc.) and includes random-access memory (RAM), dynamic random access memory (DRAM), and synchronous dynamic random access memory (SDRAM), among others. Non-volatile memory can provide persistent data by retaining stored data when not powered and can include NAND flash memory, NOR flash memory, read only memory (ROM), Electrically Erasable Programmable ROM (EEPROM), Erasable Programmable ROM (EPROM), and resistance variable memory such as phase change random access memory (PCRAM), resistive random access memory (RRAM), and magnetoresistive random access memory (MRAM), among others.
Flash memory devices can include a charge storage structure, such as is included in floating gate flash devices and charge trap flash (CTF) devices, which may be utilized as non-volatile memory for a wide range of electronic applications. Flash memory devices may use a one-transistor memory cell that allows for high memory densities, high reliability, and low power consumption.
Memory cells in an array architecture can be programmed to a target state. For example, electric charge can be placed on or removed from the floating gate of a memory cell to put the cell into one of a number of data states. For example, a single level cell (SLC) can be programmed to one of two data states representing one of two units of data (e.g., 1 or 0). Multilevel memory cells (MLCs) can be programmed to one of more than two data states. For example, an MLC capable of storing two units of data can be programmed to one of four data states, an MLC capable of storing three units of data can be programmed to one of eight data states, and an MLC capable of storing four units of data can be programmed to one of sixteen data states. MLCs can allow the manufacture of higher density memories without increasing the number of memory cells since each cell can represent more than one unit of data (e.g., more than one bit). However, MLCs can present difficulties with respect to sensing operations as the ability to distinguish between adjacent data states may deteriorate over time and/or operation.